1. Field of the Invention
In general, the present invention relates to systems and methods that enable medical personnel to select the proper radiation dosage for the particular needs of a patient. More particularly, the present invention relates to software applications that graphically plot acceptable radiation dose ranges.
2. Prior Art Description
There are many medical conditions that can be treated with radiation therapy. However, one of the most important applications of radiation therapy is its use in treating cancer inside the body. If cancer cells can be located within the human body, then those cancer cells can be targeted with beams of radiation. The radiation carries enough energy to kill the cancer cells as the radiation impinges upon the cancer cells. In this manner, cancer cells can be killed deep within tissue masses without the need for surgery.
The radiation beams begin at different physical points. Each individual radiation beam has a low dose that is insufficient to damage cells by itself. In this manner, the beams of radiation can reach the cancer cells without damaging healthy tissue along the path. The multiple beams of radiation all converge at the point of the cancer cells. The combined dose from the multiple beams of radiation then becomes sufficient to kill the cancer cells.
A problem associated with radiation therapy is that the level of radiation increases as the beams of radiation approach the treatment area. Consequently, the tissue surrounding the tumor is subjected to significant levels of radiation. Likewise, the tissue along each path of the radiation beams is also subjected to some radiation dose.
No two cancers are alike. Each cancer patient has cancer cells that are unique in location and mass to that patient. As such, the best way to direct beams of radiation onto cancer cells has become a complicated science. Physicians and dosimetrists must determine where to position the beams of radiation during radiation therapy in order to have the maximum effect on the cancer cells and the minimal effect on surrounding healthy tissue. Doctors and dosimetrists also try to avoid radiation dose to critical organ tissue, provided that tissue is healthy.
In the prior art, the manner in which a physician or dosimetrist plans a course of radiation therapy is a three step process. In the first step, the physician pinpoints the exact location of the cancer cells to be targeted. This is traditionally done using three-dimensional body imaging equipment, such as an MRI scan, a CAT scan, a PET scan or the like. Once the physician locates the target cancer cells, the dosimetrist develops a treatment plan and a dose volume histogram (DVH). The development of the dose volume histogram is the second step. The physician utilizes the dose volume histograms to evaluate the dose distribution of tissue in and around the targeted cancer cells. The dosimetrist can alter the dose, position, and direction of the various radiation beams to develop a plan that will kill the targeted cancer cells, yet minimize dose to surrounding tissue, especially critical organ tissue. In the last step, the radiation equipment is programmed to the settings developed using the treatment plan. The equipment is then ready for use on the patient.
In the prior art, the total dose of radiation is divided into a number of fractional doses, to be delivered on a daily or weekly basis. The number of fractions is defined as the number of partial treatments the patient will receive. The maximum tolerated total dose is a nonlinear function of the number of fractions. When the number of fractions is large, like 25 or 40, a higher total dose can be used than if the number of fractions is small like 1 or 5. Conversely, a large dose per fraction can obliterate certain tumors, but then the number of fractions would need to be small. Part of the problem associated with prior art techniques is that a systematic way of visualizing treatment outcomes as a function of the number of fractions is needed.
Furthermore, such prior art techniques do not have facility to overlay information from historical treatment outcomes onto the current treatment plan to help evaluate the risk associated with the dose to critical structures.
A need therefore exists for a system and method that can assist a physician and dosimetrist in optimizing the radiation therapy dose distribution to maximize effectiveness while minimizing collateral radiation dosage. A need also exists for a system and method that can actively inform a physician and/or dosimetrist that the settings selected for the radiation therapy surpass safe levels for any region of healthy tissue along the various radiation beam paths. These needs are met by the present invention as described and claimed below.